The study hypothesis is that breast arterial calcification (BAC) seen on mammograms can identify women with an increased risk of coronary artery disease (CAD). Annual mammograms are now routinely obtained on nearly 70% of women over forty years of age. The nearly 40 million examinations performed every year could be used to evaluate for BAC without any additional cost or change in current mammographic techniques. Identification of women with BAC has potential to substantially decrease the rate of heart attack and sudden death due to CAD in asymptomatic women. Before BAC can be used in a clinical setting, the age-specific prevalence of BAC needs to be fully defined using state of the art mammographic techniques. BAC then needs to be compared with well understood CAD risk factors and measures of coronary atherosclerosis. While this could be accomplished in a prospective study, we can attain the same goals using data already acquired in the Epidemiology of Coronary Calcification (ECAC) Study. Using this preexisting database fulfills one of the requirements for this NHLBI R21 Grant. Coronary artery calcification (CAC) is detected non-invasively on electron beam computed tomographic (EBCT) exams. CAC quantity correlates well with atherosclerotic plaque area. This population-based study has been instrumental in establishing the distribution of presence and quantity of CAC as well as the predictors of CAC. The database includes clinical and laboratory assessments of CAD risk factors, results of EBCTs, and findings on physical examinations. It will ultimately include information on adverse clinical events. There are 612 female participants who had one or more mammograms during the 12-year history of that study. Many women had 10 or more mammograms. The proposal is to evaluate all of these mammograms for BAC and compare the findings with information already in the database. The combination of newly acquired data from mammograms with the existing data allows this to be a very comprehensive study and still be completed in the two-year time period and with the funding constraints of this R21 grant. The findings can then be used to help design a future study to prospectively evaluate the impact of instituting preventive and early therapeutic measures for CAD in asymptomatic women with the appropriate features of BAC on mammography.